The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Shorten tries to steal Turnbull's moment

It was a case of the magic Medicare bus at Labor's second election campaign launch.

Opposition Leader Bill Shorten rallied 300 of the assembled party faithful at the Brisbane Convention Centre on Sunday, in an attempt to steal some of the spotlight from Prime Minister Malcolm Turnbull's official Liberal campaign launch in Sydney.

Mr Shorten stood on a podium in front of his campaign bus that has criss-crossed the nation with a picture of his face on the sides.

After welcoming another Bill - former Labor leader Bill Hayden, one of the architects of Medicare - Mr Shorten said there was one message to "drive home" as the election campaign's eight week marathon became a six day sprint.

"Bill Shorten and Labor will save Medicare," read the new message on the bus as the sheet was swept away.

He referred to parents coping with a sick child.

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"In that moment you would give up everything, you would sell the shirt off your back and the roof over your head, but because of Medicare, you don't have to," Mr Shorten said, because Australians could get the medical care they need, when they need it.

The federal government was pretending its Medicare privatisation committee was a social club, Mr Shorten said.

He declared it would be the last Sunday of a Liberal government nationally.

Mr Shorten sharpened his attack on Mr Turnbull's leadership and disunity within government ranks, claiming he was being held prisoner within his party.

"Those Liberals in that party are sharpening their weapons of revenge for the impending civil war," Mr Shorten said.

Mr Shorten will travel to Gladstone to campaign in the Liberal seat of Flynn on Sunday afternoon before heading to Melbourne.